1. Field of the Invention
This invention relates to an image reading apparatus and power control method. More particularly, this invention relates to an image reading apparatus which optically reads, e.g., an image printed on a sheet-like printing medium, and a power control method applied to the apparatus.
2. Description of the Related Art
Conventionally, some image reading apparatuses such as a scanner comprise an LCD (Liquid Crystal Display), and display text information and an image on the LCD screen upon reading an image, as disclosed in Japanese Patent Publication Laid-Open No. 2002-016744. Some LCD implement backlighting with low power consumption by controlling to time-divisionally turn on three (R, G, and B) light sources of the backlight of a color LCD, as disclosed in Japanese Patent Publication Laid-Open No. 5-346570.
In the prior arts, however, the backlight of the LCD is turned on upon reading an image, and then text information and an image are displayed. Thus, power for driving the LCD is required in addition to driving power necessary to read an image by the image reading apparatus.
In an image reading apparatus which is driven upon reception of power supply via a USB bus, the backlight of the LCD cannot be turned on in image reading due to the power limitation (5V, 500 mA) of the USB bus.